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We quantified the distribution of nitrogen (N), dry-matter (biomass) and of soil-applied 15 N in tree and soil compartments in five naturally-growing 20-year-old oak trees. After applying 15 N solution to soil at the base of the trees in spring, all the trees were felled in the fall, their root system excavated, biomass, nitrogen and 15 N content measured in all compartments. Xylem rings-compartment contains most biomass (47%) while branches and coarse-root contains most nitrogen (29% and 14% respectively). The labelled 15 N absorbed throughout the vegetation season, was found in all compartments except the heartwood. The majority of recovered 15 N was in the leaves (24%). Some often overlooked compartments (coarse root, stump, xylem and other branches) together recovered 45% of the 15 N. 15 N was found in all the sapwood rings, from the ring formed in the current year up to 10 year-old rings, marking the limit of the heartwood. More 15 N was found in the younger rings compared to older rings. The 15 N allocated to ancient rings can originate from different, non-mutually exclusive, sources: whether directly from the soil via the 15 N uptake throughout the vegetation season and transport in the xylem sap, from the autumnal resorption of 15 N first allocated to the leaves, or from the 15 N mobility once allocated to the forming ring to older rings through ray parenchyma. With about 6% of the initial 15 N retrieved in the microbial biomass at the end of the growing season, we confirmed the role of microbial biomass as forest nitrogen sink.

Aims We simultaneously quantified the fate of soil absorbed mineral nitrogen in different tree compartments along with nitrogen immobilization by microorganisms during spring in 20-year-old oak trees. Methods A soil-applied 15 N solution was traced in situ into the fine roots, medium roots, xylem, phloem, branches, leaves, extractable soil, and microbial biomass before and after budburst, until LAI maximum was reached. Results During the three weeks following the labeling, around half of the 15 N applied was incorporated into the microbial biomass while the leafless trees absorbed less than 10% of the 15 N. Before and after budburst, the microbial compartment was the main pool of 15 N, and yet the soil-absorbed 15 N still significantly contributed to the leaf nitrogen pool at budburst. This contribution in leaves sharply increased in the days following budburst. Conclusion The potential competition for mineral nitrogen between trees and the soil microbial biomass is strong during spring. The dependence of the leaf nitrogen pool to internal or external stocks of nitrogen at budburst could be conditioned by environmental conditions.

Blue carbon ecosystems, such as mangroves, tidal marshes, and seagrasses, are important for climate mitigation. As carbon sinks, they often exhibit higher per hectare carbon storage capacity and sequestration rates than terrestrial systems. These ecosystems provide additional benefits, including enhancing water quality, sustaining biodiversity, and maintaining coastal resilience to climate change impacts. The widespread loss of blue carbon ecosystems due to anthropogenic activities can contribute to increasing carbon emissions globally. Monetizing blue carbon through carbon credits offers an avenue to generate revenue and incentivize conservation and restoration efforts. However, limited data on project costs and carbon benefits make prioritization of blue carbon projects challenging. To address these challenges, we have developed, in collaboration with blue carbon experts, the Blue Carbon Cost Tool. This is a user-friendly interface enabling comparison of three core market project components – 1) carbon credit estimation, 2) project cost estimation, and 3) a qualitative, non-economic feasibility assessment – to assess and compare potential for blue carbon projects. Tool simulations with data available from nine countries demonstrate (a) how factors such as country, ecosystem type and project scale drive variability, (b) the need for local or project-specific data to enhance accuracy and reduce uncertainty, particularly in tidal marsh and seagrass systems, and (c) that higher price tolerance or upfront capital is needed to bridge implementation and maintenance cost gaps. The Blue Carbon Cost Tool can aid project developers and investors to better understand market opportunity and the resources needed to develop high quality blue carbon market projects.

We simultaneously quantified the fate of soil absorbed mineral nitrogen in different tree compartments along with nitrogen immobilization by microorganisms during spring in 20-year-old oak trees. A soil-applied .sup.15N solution was traced in situ into the fine roots, medium roots, xylem, phloem, branches, leaves, extractable soil, and microbial biomass before and after budburst, until LAI maximum was reached. During the three weeks following the labeling, around half of the .sup.15N applied was incorporated into the microbial biomass while the leafless trees absorbed less than 10% of the .sup.15N. Before and after budburst, the microbial compartment was the main pool of .sup.15N, and yet the soil-absorbed .sup.15N still significantly contributed to the leaf nitrogen pool at budburst. This contribution in leaves sharply increased in the days following budburst. The potential competition for mineral nitrogen between trees and the soil microbial biomass is strong during spring. The dependence of the leaf nitrogen pool to internal or external stocks of nitrogen at budburst could be conditioned by environmental conditions.

Tidal marshes are threatened coastal ecosystems known for their capacity to store large amounts of carbon in their water-logged soils. Accurate quantification and mapping of global tidal marshes soil organic carbon (SOC) stocks is of considerable value to conservation efforts. Here, we used training data from 3710 unique locations, landscape-level environmental drivers and a global tidal marsh extent map to produce a global, spatially explicit map of SOC storage in tidal marshes at 30 m resolution. Here we show the total global SOC stock to 1 m to be 1.44 Pg C, with a third of this value stored in the United States of America. On average, SOC in tidal marshes’ 0–30 and 30–100 cm soil layers are estimated at 83.1 Mg C ha −1 (average predicted error 44.8 Mg C ha −1 ) and 185.3 Mg C ha −1 (average predicted error 105.7 Mg C ha −1 ), respectively. A new study shows the total global SOC stock of 1 m in the world’s tidal marshes to be 1.44 Pg C. On average, SOC in tidal marshes’ 0–30 cm and 30–100 cm soil layers are estimated at 83.1 Mg C ha −1 and 185.3 Mg C ha −1 , respectively.

Aims: We simultaneously quantified the fate of soil absorbed mineral nitrogen in different tree compartments along with nitrogen immobilization by microorganisms during spring in 20-year-old oak trees. Methods: A soil-applied(15)N solution was traced in situ into the fine roots, medium roots, xylem, phloem, branches, leaves, extractable soil, and microbial biomass before and after budburst, until LAI maximum was reached. Results: During the three weeks following the labeling, around half of the(15)N applied was incorporated into the microbial biomass while the leafless trees absorbed less than 10% of the(15)N. Before and after budburst, the microbial compartment was the main pool of(15)N, and yet the soil-absorbed(15)N still significantly contributed to the leaf nitrogen pool at budburst. This contribution in leaves sharply increased in the days following budburst. Conclusion: The potential competition for mineral nitrogen between trees and the soil microbial biomass is strong during spring. The dependence of the leaf nitrogen pool to internal or external stocks of nitrogen at budburst could be conditioned by environmental conditions.

Aims: We simultaneously quantified the fate of soil absorbed mineral nitrogen in different tree compartments along with nitrogen immobilization by microorganisms during spring in 20-year-old oak trees. Methods: A soil-applied(15)N solution was traced in situ into the fine roots, medium roots, xylem, phloem, branches, leaves, extractable soil, and microbial biomass before and after budburst, until LAI maximum was reached. Results: During the three weeks following the labeling, around half of the(15)N applied was incorporated into the microbial biomass while the leafless trees absorbed less than 10% of the(15)N. Before and after budburst, the microbial compartment was the main pool of(15)N, and yet the soil-absorbed(15)N still significantly contributed to the leaf nitrogen pool at budburst. This contribution in leaves sharply increased in the days following budburst. Conclusion: The potential competition for mineral nitrogen between trees and the soil microbial biomass is strong during spring. The dependence of the leaf nitrogen pool to internal or external stocks of nitrogen at budburst could be conditioned by environmental conditions.

Tidal marsh ecosystems are heavily impacted by human activities, highlighting a pressing need to address gaps in our knowledge of their distribution. To better understand the global distribution and changes in tidal marsh extent, and identify opportunities for their conservation and restoration, it is critical to develop a spatial knowledge base of their global occurrence. Here, we develop a globally consistent tidal marsh distribution map for the year 2020 at 10-m resolution. Global 2020 Tidal marshes To map the location of the world’s tidal marshes we applied a random forest classification model to earth observation data from the year 2020. We trained the classification model with a reference dataset developed to support distribution mapping of coastal ecosystems, and predicted the spatial distribution of tidal marshes between 60°N to 60°S. We validated the tidal marsh map using standard accuracy assessment methods, with our final map having an overall accuracy score of 0.852. We estimate the global extent of tidal marshes in 2020 to be 52,880 km2 (95% CI: 32,030 to 59,780 km2) distributed across 120 countries and territories. Tidal marsh distribution is centred in temperate and Arctic regions, with nearly half of the global extent of tidal marshes occurring in the temperate Northern Atlantic (45%) region. At the national scale, over a third of the global extent (18,510 km2; CI: 11,200 – 20,900) occurs within the USA. Our analysis provides the most detailed spatial data on global tidal marsh distribution to date and shows that tidal marshes occur in more countries and across a greater proportion of the world’s coastline than previous mapping studies. Our map fills a major knowledge gap regarding the distribution of the world’s coastal ecosystems and provides the baseline needed for measuring changes in tidal marsh extent and estimating their value in terms of ecosystem services

Tidal marshes are threatened coastal ecosystems known for their capacity to store large amounts of carbon in their water-logged soils. Accurate quantification and mapping of global tidal marshes soil organic carbon (SOC) stocks is of considerable value to conservation efforts. Here, we used training data from 3,710 unique locations, landscape-level environmental drivers and a newly developed global tidal marsh extent map to produce the first global, spatially-explicit map of SOC storage in tidal marshes at 30 m resolution. We estimate the total global SOC stock to 1 m to be 1.44 Pg C, with a third of this value stored in the United States of America. On average, SOC in tidal marshes’ 0-30 and 30-100 cm soil layers are estimated at 83.1 Mg C ha-1 (average predicted error 44.8 Mg C ha-1) and 185.3 Mg C ha-1 (average predicted error 105.7 Mg C ha-1), respectively. Our spatially-explicit model is able to capture 59% of the variability in SOC density, with elevation being the strongest driver aside from soil depth. Our study reveals regions with high prediction uncertainty and therefore highlights the need for more targeted sampling to fully capture SOC spatial variability.